"They accused me of filming illegally and demanded ID," she said. "Once they had it they said that's her."

The authorities confirmed they had been expelled "for applying for tourist visas under false pretences".

"Huwaida Arraf and Radhika Sainath arrived in Bahrain in the last few days and obtained tourist visas upon arrival at the airport," the government said. "However, once in Bahrain, they declared their intentions to join demonstrations in order to report on them. Arraf and Sainath were picked up at an illegal demonstration in Manama this afternoon."

Police fired tear gas and sound grenades to break up protests by anti-government demonstrators on Sunday as they tried to march towards Manama's Pearl Roundabout, centre of a failed uprising last year.

The women were showing solidarity on the eve of the first anniversary of protests led mainly by the Shia majority for democratic reforms in the Gulf Arab state. An official said they would be deported for giving false information about their trips on entering the country.

The advocacy group Witness Bahrain said both Arraf and Sainath are human rights lawyers. They were in the Middle Eastern country as part of an effort to have more civilians from different nations on the ground to monitor the situation.

Miss Sainath said the pair were part of Witness Bahrain. In an article before the rally she said: "The government would behave differently if Americans and Europeans were watching."Our team came together: attorneys, human rights activists, social workers, journalists and others who had experience with nonviolent resistance and democracy movements in Mexico, Palestine, Pakistan and the United States," she said